Methods of reducing precipitation from acid solutions

Abstract

Methods and compositions for reducing the precipitation of metal sulfides from acid solutions are provided. The methods basically comprise reducing the precipitation of metal sulfide compounds from an aqueous acid solution when the solution dissolves sulfide and metal ions by combining at least one oxime with the acid solution in an amount whereby the oxime preferentially reacts with sulfide ions in the solution and thereby prevents the sulfide ions from reacting with metal ions therein.

What is claimed is: 
     
       1. A method of reducing the precipitation of metal sulfide compounds from an acid solution when said acid solution contains dissolved sulfide and metal ions comprising reacting at least one oxime of the formula R--CH═N--OH wherein R is an alkyl radical having from 1 to about 7 carbon atoms or a phenyl radical contained in said acid solution with said dissolved sulfide ions in said acid solution to thereby prevent said sulfide ions from reacting with dissolved metal ions therein. 
     
     
       2. The method of claim 1 wherein said oxime is present in said acid solution in an amount in the range of from about 0.05% to about 20% by weight of said acid solution and oxime. 
     
     
       3. The method of claim 1 wherein said acid is selected from inorganic acids, organic acids and mixtures thereof. 
     
     
       4. The method of claim 1 wherein said acid comprises an inorganic acid. 
     
     
       5. The method of claim 4 which further comprises the step of including an organic acid in said acid solution in an amount in the range of from about 2.5% to about 20% by weight of water, inorganic acid and organic acid in said solution. 
     
     
       6. The method of claim 5 wherein said organic acid is selected from the group consisting of formic acid, acetic acid, citric acid, lactic acid, thioglycolic acid and glycolic acid. 
     
     
       7. The method of claim 5 wherein said organic acid is glycolic acid. 
     
     
       8. A method of reducing the precipitation of metal sulfide compounds from an aqueous acid solution used for acid treating a sour well when said acid solution contains dissolved sulfide and metal ions comprising reacting acetaldoxime contained in said acid solution with said dissolved sulfide ions in said solution to thereby prevent said sulfide ions from reacting with dissolved metal ions therein. 
     
     
       9. The method of claim 8 wherein said acetaldoxime is present in said acid solution in an amount in the range of from about 0.05% to about 20.0% by weight of said acid solution and acetaldoxime. 
     
     
       10. The method of claim 9 wherein said acid is selected from inorganic acids, organic acids and mixtures thereof. 
     
     
       11. The method of claim 9 wherein said acid comprises an inorganic acid selected from the group consisting of hydrochloric acid, hydrofluoric acid, fluoboric acid and mixtures thereof present in said aqueous acid solution in an amount in the range of from about 5% to about 30% by weight of water and inorganic acid in said solution. 
     
     
       12. The method of claim 11 which further comprises the step of including an organic acid in said acid solution in an amount in the range of from about 2.5% to about 20% by weight of water, inorganic acid and organic acid in said solution. 
     
     
       13. The method of claim 12 wherein said organic acid is selected from the group consisting of formic acid, acetic acid, citric acid, lactic acid, thioglycolic acid and glycolic acid. 
     
     
       14. The method of claim 12 wherein said organic acid is glycolic acid.